hi

when we are reading about interrupts it says when an interrupt occur during normal cycle scan of cpu it causes operating system call related OB ,and if related OB was downloaded to cpu it will not go to stop mode,i have seen programmer downloaded any OB like OB 121,80,86,... to plc but remained OB vacant and there is nothing in them,if i  download OB without  any program in it ,when related interrupt occur can it prevent stopping cpu?

regards

Hello,

Perhaps the following topics might help:

1-Which organization blocks do you need for error handling in STEP 7 V5.5?

2-Which organization blocks do you have to load into the CPU to ensure that the CPU does not go into the "STOP" status when a remote I/O fails?

Hello hamed;

To add to the information provided by Online Tech (Moh. Ibrahim), there are dedicated organization blocks (OBs) that are known as "diagnostic OBs". they are used to gather information from the CPU's OS whenever a fault is detected during opertion.

The diagnostic OBs are OB 80 to 88, OB 121 and OB 122; see the screenshot below, taken from the System and Standard Functions manual:

https://support.industry.siemens.com/cs/document/109751826/simatic-system-software-for-s7-300-400-system-and-standard-functions-volume-1-2?dti=0&lc=en-WW

Chapter 1 of the manual examines the different types of OBs available to structure a Siemens PLC program; you should examine the structure of the local data of each diagnostic OB, for example OB 86 (Rack Failure OB) on page 66. The local data registers are used to gather data from the CPU about a fault, if the error is linked to a lost remote I/O rack (Profibus or Profinet). While this OB is being processed, without any internal programming, the CPU will continue working, even though a fault has been detected, because it is communicating with this OB 86 local data. Once it has gathered the information and placed it in the diagnostic buffer, it will return control to OB1 and continue processing the program instructions. So it will not go to STOP, but the diagnostic LEDs will be activated to indicate there is an intervention required by the programmer.

The following discussion provides information on the same subject, it could be interesting to you:

https://support.industry.siemens.com/tf/WW/en/posts/problem-on-cpu-315-2dp/90455?page=0&pageSize=10

Hope this helps,

Daniel Chartier

great!! exactly i have got my questions answer

it is my honor that i can communicate with so high experienced and knowledgeable friends like you in this forum